Combined or individual administration of branched-chain amino acids following total hepatectomy in the rat: effects on amino acids and indoleamines in brain.

The effects of infusing leucine, isoleucine, and valine, either singly or together into rats after total hepatectomy were compared. Hepatectomized rats receiving only glucose had high concentrations in plasma of most amino acids, except the branched-chain amino acids; in brain, the concentrations of glutamine, most large neutral amino acids and 5-hydroxyindoleacetic acid were greatly elevated. When all three branched-chain amino acids were infused, the rise in plasma concentration of essential amino acids and tyrosine was significantly reduced. Infusion of isoleucine did not significantly reduce the concentrations of any essential amino acid in plasma while valine reduced lysine, methionine and tryptophan and leucine reduced only methionine. In contrast, all infusions of branched-chain amino acids, either singly or in combination, reduced brain levels of other large neutral amino acids. Infusion of branched-chain amino acids greatly elevated the plasma concentrations of glutamine and alanine and prevented the decrease in brain concentrations of glutamic acid, a neurotransmitter.